INFR 2830U Assignment 1

Problem 1

Suppose the hypothetical processor of Figure below also has two I/O instructions:

0001 - Local AC from Memory
0010 - Store AC to Memory
0101 - Add to AC from Memory
0111 – Subtract Memory from AC
1001 - Load AC from I/O Device
1010 - Store AC to I/O Device

See figure image: See image.

In these cases, the 12-bit address identifies a particular external device.

Show the program execution (using the format of Figure 1.4 in the next page) for the following program:

• Load AC from device A.
• Subtract contents of memory location 941.
• Store AC to memory 940.

Assume that the next value retrieved from device A is 4 and that location 941 contains a value of 3. see image.

Problem 2

Assume that at time 5 no system resources are being used except for the processor and memory. Now consider the following events:

Time Event
5 P1 executes a command to read from disk unit 3
15 P5’s time slice expires
18 P3 executes a command to read from disk unit 2
20 P7 executes a command to write to disk unit 3
24 P5 executes a command to write to disk unit 3
28 P5 is swapped out
33 An interrupt occurs from disk unit 3: P1’s read is complete
36 An interrupt occurs from disk unit 2: P3’s read is complete
38 P8 terminates
40 An interrupt occurs from disk unit 3: P5’s write is complete
44 P5 is swapped back in
48 An interrupt occurs from disk unit 3: P7’s write is complete

For each time identify which state each process is in. If a process is blocked, further identify the event on which is it blocked.

Problem 3

If a process exits and there are still threads of that process running, will they continue to run?

Problem 4

Figure 3.9a below contains six states. In principle, one could draw a transition between two states, for a total of 14 different possible transitions (not all showing below).

• List all of the possible transitions and give an example of what could cause each transition.
• List few impossible transitions and explain why.

See figure image. See image.